1. Field of the Invention
This invention relates in general to transceivers for communication systems, and more particularly to a method and apparatus for maintaining component temperature in a base transceiver station (BTS).
2. Description of Related Art
The telecommunications industry is in the midst of its most dramatic set of changes since the analog telephone system was introduced more than 100 years ago. Deregulation, the Internet and new technology are reshaping the market. Users may not choose between multiple service providers; digital technology is pervasive; and new data services are fueling overall growth for telecommunications services. Further, data services such as dial-up Internet access, digital private lines and even some virtual private network services are typically offered at a fixed price. In some cases this results in a great value for the customer. Such growth is fueling many research programs and expanding the technology opportunities for all manufacturers.
The worldwide third-generation (3G) mobile communications standards being developed by the International Telecommunications Union, through its International Mobile Telecommunications 2000 initiative, are expected to not only provide for global roaming among multiple countries and networks, but also for a smorgasbord of compute-intensive and signal processing-intensive services, delivered at data rates of up to 2 Mbits/second. These services may include full-motion video, Web browsing and video-conferencing, as well as the more pedestrian fax, e-mail access and paging services associated with second-generation systems.
Wireless carriers are hoping the new competition will help the market grow. Currently, about 53 million people subscribe to wireless services. However, the important thing to consumers is that they have access to communications they can count on. End users want to really know that they can count on their communications devices and the wireless networks.
One problem encountered with wireless networks is cold starts for the base station. Within a base station, a transceiver is used for transmitting and receiving user signals. The transceiver includes many components for processing user calls and for controlling the calls. The power amplifier provides a fundamental function of the base station in a wireless communications system. The signal level must be amplified enough to overcome the inherent losses during wireless transmission so that it can be received by the mobile stations or handsets. The design requirements for RF power amplifiers include high output power and good efficiency.
The main purpose of the power amplifier is to deliver power into the antenna as efficiently as possible. Accordingly, power amplifiers are normally biased to most effectively deliver the power to the antenna, and therefore do not generate any heat which is not necessary for the accomplishment of this task. Often, in fact, amplifiers are fitted with large heat-sinks or external cooling systems to prevent heat building up which may damage the power amplifier as well as the other components.
Nevertheless, in a base station environment, temperature considerations are often reversed. For example, base stations are subjected to outside temperatures that often cause the interior temperature, and consequently the temperature of the components themselves, to fall below minimum temperature de-ratings. Because of the minimum temperature de-ratings on the components used in the BTS, the BTS has to be pre-heated prior to being fully commissioned and operational.
Accordingly, the current solution is to heat the internal air in the base station. This in turn heats up the surrounding metal casings and the internal temperature of the BTS and components is increased. Once the components have reached a suitable temperature, the base station is then ready to be commissioned.
However, the process of raising the internal temperature of the components is a very lengthy process. Often, internal printed-circuit board (PCB) mounted heating elements, flexible heating pads or hot air blowers are used. Nevertheless, the cost of such solutions are substantial.
It can be seen that there is a need for a method and apparatus that reduces or eliminates the time required for raising the internal temperature of components in a base station transceiver.
It can also be seen that there is a need for a method and apparatus that raises the internal temperature of components in a base station transceiver without incurring substantial cost.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for maintaining component temperature in a base station transceiver.
The present invention solves the above-described problems by providing a method and apparatus that reduces or eliminates the time required for raising the internal temperature of components in a base station transceiver without incurring substantial cost.
A base station transmitter in accordance with the principles of the present invention includes power amplifier for receiving a signal at an input and providing an amplified signal at an output and a switch, coupled to the input of the power amplifier, for switching between a first and a second bias circuit in response to a control signal, wherein the first bias circuit comprises an RF bias circuit for providing normal RF bias to the power amplifier and the second bias circuit is a cold start bias circuit for providing a cold start bias to the power amplifier.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the power amplifier comprises a power transistor.
Another aspect of the present invention is that the base station transmitter further includes bias elements coupled to the power transistor for controlling the gain and frequency response of the power transistor.
Another aspect of the present invention is that the base station transmitter further includes a plurality of components and wherein the cold start bias circuit causes the power transmitter to substantially increase an amount of heat dissipated by the power amplifier to heat the components above temperature de-ratings for the components.
Another aspect of the present invention is that the base station transmitter further includes a temperature monitor and a plurality of components, the temperature monitor comparing a measured temperature to a minimum and a maximum reference temperature.
Another aspect of the present invention is that the temperature monitor provides a signal for engaging the switch causing the cold start bias circuit to be selected by the switch when the measured temperature is less than the minimum reference temperature.
Another aspect of the present invention is that the temperature monitor provides a signal for disengaging the switch causing the RF bias circuit to be selected by the switch when the measured temperature is greater than the minimum reference temperature.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.